1. Field of the Invention
The present invention relates to the field of devices that produce pressurized hydraulic fluids, and more particularly, to devices that utilize compressed air to drive a reciprocating air piston in order to produce pressurized hydraulic fluid for purposes such as actuating hydraulic lift cylinders.
2. Description of the Related Art
Although there are a number of issued U.S. patents and patent applications that describe air-to-hydraulic fluid pressure amplifiers, none of these prior-art inventions includes the novel features of the present invention, which comprises dual hydraulic rams, custom-designed end-of-stroke sensors for the air piston, and an easily replaceable annular seal for the hydraulic rams.
U.S. Pat. No. 4,407,202 (McCormick, 1983) discloses a hydraulically activated dumping system for railway cars. In one embodiment, the invention employs a booster pump that is comprises a large bore air cylinder connected to a small bore hydraulic cylinder for the purpose of using low-pressure compressed air to provide high-pressure hydraulic fluid. The air cylinder is reciprocated to pressurize the hydraulic fluid. The invention comprises a single hydraulic ram, which produces one pressure stroke of hydraulic fluid for each back-and-forth cycle of the piston in the air cylinder.
U.S. Pat. No. 5,261,333 (Miller, 1993) discloses an automated ballast door mechanism for use with a railroad hopper car. The invention comprises pressurized hydraulic fluid, which is produced by an air-powered motor that drives a hydraulic fluid pump. The details of the motor and pump are not disclosed.
U.S. Pat. No. 7,051,661 (Herzog et al., 2006), U.S. Pat. No. 7,735,426 (Creighton et al., 2010), U.S. Pat. No. 7,891,304 (Herzog et al., 2011) and U.S. Pat. No. 8,915,194 (Creighton et al., 2014) are related patents that disclose discharge control systems for railroad cars. Some embodiments of the inventions disclosed in these patents employ air cylinder actuators and hydraulic motors, but no air-to-hydraulic fluid pressure amplifiers are described.
U.S. Pat. No. 7,328,661 (Allen et al., 2008) discloses a control device for a railroad car door. This invention comprises an air piston actuator but does not comprise hydraulic components.
U.S. Pat. No. 7,389,732 (Taylor, 2008) discloses a mechanism for selectively operating hopper doors of a railroad car. This invention does not comprise hydraulic components.
U.S. Pat. No. 6,192,804 (Snead, 2001) discloses a hydraulically actuated railway car dumping system that comprises a pneumatic-to-hydraulic pressure amplifier. The pressure amplifier of this invention comprises two pneumatic pistons in two separate pneumatic cylinders that are linked to a single, double-acting hydraulic pump via a pivoting lever arm.
U.S. Pat. No. 8,701,565 (Creighton et al., 2014) discloses devices for powering railroad car doors. In one embodiment, an air motor is used to drive a hydraulic pump (FIG. 13), but no details of an air-to-hydraulic pressure amplifier are disclosed.